Due to the anisotropic characteristics of liquid crystal material, a liquid crystal device usually only responds to polarized light. So when a crystal liquid lens is used in an imaging device, a polarizing device such as a polarizing plate or a polarizer is required to polarize the incident light. But the use of the polarizer will lose more than half of the incident light intensity. Thus, in a darker environment, there may not be enough light to reach the image sensor, causing decreased signal to noise ratio and lowered image quality.
To avoid the use of the polarizer, a lens group composed of multiple superimposed liquid crystal lenses with their initial alignment of the liquid crystal layers perpendicular to each other may be used in the imaging system. Or a liquid crystal lens superimposed by multiple liquid crystal layers with their initial alignment perpendicular to each other may be designed for the imaging system. Each liquid crystal lens or each liquid crystal layer processes respectively polarization component of an arbitrary polarization state in two perpendicular directions, thus it can be applied to the situation of arbitrary polarization state. But such solution has the following problems.
For the solution with multiple superimposed liquid crystal lenses or multiple superimposed liquid crystal layers, due to the increased number of the liquid crystal lenses or liquid crystal layers, the manufacturing cost of the liquid crystal lens may be greatly increased. The increased number of liquid crystal lenses or liquid crystal layers may also greatly increase the thickness of the device, making it difficult for the liquid crystal lens imaging apparatus to be implemented into mobile devices such as mobile phones, tablet computers, etc. Moreover, because each liquid crystal lens or each liquid crystal layer is located at different positions in the imaging system, the propagation behavior of the two components of the polarized light is not exactly the same, which may reduce the imaging quality of the system.
The disclosed methods and systems are directed to solve one or more problems set forth above and other problems, including how to directly generate high quality images with the liquid crystal lens without the polarizer and to reduce the thickness of the lens structure at the same time.